The use of periodic, uniformly spaced relief microstructures in imaging, printing, and as photosensitive elements and micro reaction vessels, etc. has been long known in the art. See, e.g., U.S. Pat. No. 4,362,806 to Whitmore; U.S. Pat. No. 4,366,235 to Land; U.S. Pat. No. 4,386,145 to Gilmour, May 31, 1983; James J. Cowan, W. D. Slafer, “The Recording and Replication of Holographic Micropatterns for the Ordering of Photographic Emulsion Grains in Film Systems,” J. Imaging Sci. 31, 100-107 (1987); W. D. Slafer, V. K. Walworth, A. B. Holland, J. J. Cowan, “Investigation of Arrayed Silver Halide Grains, J. Imaging Sci. 31, 117-125 (1987); U.S. Pat. No. 4,663,274 to W. D. Slafer et al.; and, V. Walworth, W. D. Slafer, A. B. Holland, “Thin Layer Coalescence of Silver Halides”, J. Imaging Sci. 31, 108-116 (1987).
More recently, such microstructures have been used in electronics and electrophoretic displays (EPDs). See, e.g., Sachin Bet and Aravinda Kar, “Thin film deposition on plastic substrates using silicon nanoparticles and laser nanoforming”, Materials Science and Engineering: B, Volume 130, Issues 1-3, 15 Jun. 2006, Pages 228-23; see also U.S. Pat. No. 7,144,942 to Zang et al.; U.S. Pat. No. 7,005,468 to Zang et al.; U.S. Pat. No. 6,972,893 to Chen et al.; U.S. Pat. No. 6,933,098 to Chan-Park et al.; U.S. Pat. No. 6,906,779 to Chan-Park et al.; U.S. Pat. No. 6,873,452 to Tseng et al.; U.S. Pat. No. 6,833,177 to Chen et al.; U.S. Pat. No. 6,788,452 to Liang et al.; and, U.S. Pat. No. 6,753,067 to Chen et al.
Methods for the formation and replication of the three-dimensional relief microstructures (herein referred to as “3D patterns” or “micropatterns” or “micro-patterns”) are also well known in the prior art and may include micro-embossing, contact mask lithography, microprinting, ink jet printing, etc.
The use of 3D polymer structures for form patterned thin film electrode structures by roll-to-roll processing means is described in previous patent application by the assignee of the subject application, MicroContinuum Inc., referred to previously in the section for Related Applications.
Relief microstructures in the form of cells or cups have further been molded or embossed on substrates containing an electrically conductive layer in order to form addressable pixel elements for displays; however, the molding of such microcells in a polymeric layer results in the formation of a layer of polymer between the bottom of the cell and the conductive layer (“residual polymer layer”), which is very undesirable and detrimental in applications in which intimate contact between the conductor and the contents of the 3D pattern is required (such as for electrochemical reactions, thin film transistor (TFT) elements, diodes, etc.) and may completely prevent functionality of the device. This shortcoming of the prior art is eliminated by the methods described herein.
It is further often very desirable to form patterns in which there exists no pattern discontinuity or interruption (seams or joints), such as for a display device or electronic active matrix array, where the existence of one or more seams in an active area, for example, may result in visual or electronic defects or limitations, such as the appearance of lines in a display or interruptions in an electronic circuit. The patterning tools known to the art for forming or molding precision 3D microstructures and thin film patterns by roll-to-roll processes do not teach the means of eliminating such discontinuities, and this shortcoming of the prior art may be eliminated embodiments as described in the above-referenced U.S. patent application Ser. No. 11/509,288, entitled “Replication Tools and Related Methods and Apparatus.”
The manufacture of more complex flexible electronic devices often utilizes multi-level structures, and the alignment and registration of various elements from one layer to the next may be required in order to allow the electrical addressing of a specific element (or group of elements), or to make electrical connections between various elements (electrodes or cells, for example) in different layers. Precision multilayer alignment is routinely achieved in the batch semiconductor and electronics fields, but for the efficient, cost-effective, and high volume manufacture of many devices, continuous R2R manufacturing is very desirable. However, although registration of various pattern layers on flexible polymer films is also frequently cited as being very desirable, methods for alignment and registration of various electrodes and micropatterns formed by molding or embossing processes in continuous roll-to-roll processes is not well described or taught in the prior art.
For example, in U.S. Pat. No. 6,906,779 B2, synchronized motion of a moving non-contact photomask and a pre-formed pattern in a continuous process is discussed, but only insofar as attempting to keep the relative film speeds the same, but no mention is made of registering the patterns in the orthogonal (cross-web) direction or confirming that the patterns are aligned, or how substrate distortion is handled. Further, no mention is made here of the critical case that addresses physical contact molding of 3D structures in registration with a pre-patterned substrate. In addition, processes utilizing lithographic mask methods are significantly limited in resolution compared to that which can be achieved with physical contact patterning methods, such as imprint lithography, embossing or molding.
While the above-referenced prior art techniques may prove suitable for their intended applications, there exists a need for improved techniques, methods, systems and apparatus by which addressable 3D elements can be formed on a flexible substrate.